A system for analyzing a fluid is, for example, a system for analyzing saliva comprising a disposable cartridge and a reading apparatus. A disposable swab-stick is provided for collecting a saliva sample and for transferring the same to the disposable cartridge for providing the saliva sample to the reading apparatus for analyzing the provided saliva sample. Generally, a sealed package is provided comprising the disposable swab-stick and the disposable cartridge. In a standard procedure the cartridge is inserted into the reading apparatus and then the swab-stick is used to collect a saliva sample. When the saliva sample has been collected, it can be mixed with a buffer fluid. Subsequently, the buffered sample can be applied to the cartridge and the buffered saliva flows through a filtering section and reagent releasing section into an analyzing section, in which the saliva is analyzed by using the reader. This system for analyzing a fluid is disclosed in the article “Cozart® RapiScan Oral Fluid Drug Testing System: An Evaluation of Sensitivity, Specificity, and Efficiency for Cocaine Detection Compared with EIA and GC-MS Following Controlled Cocaine Administration”, Erin A. Kolbrich et al., Journal of Analytical Toxicology, Vol. 27, October 2003.
When the cartridge is inserted into the reading apparatus, the reading apparatus detects the presence of the cartridge and the detection electronics for analyzing the saliva sample are switched on. In the period between cartridge detection and fluid assaying or analyzing the sample needs to be collected. This collecting of the sample takes at least 30 seconds in the average and might take up to some minutes. Moreover, time is needed for handling by the operator. During this period the detection electronics are switched on. This consumes unnecessary power in the reading apparatus.